This invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of joining beam leads to electrodes of a semiconductor device.
Recently, semiconductor devices such as IC's and LSI's have been intensively introduced into the fields of various electric household appliances and industrial machinery. To some resources, same electricity or expand the range of application, such electric household appliances and industrial machinery have been gradually downsized or made portable.
To meet this downsizing trend, in the field of semiconductors, packages are required to be smaller and thinner. A silicon slice after a diffusion process and an electrode wiring process is cut into chips each in the unit of a semiconductor device, electrode leads are taken out from the aluminum electrode terminals disposed around each chip to external terminals for ease of handling, and chips are packaged for mechanical protection. Usually, for packaging of these semiconductor devices, Dual-in-Line (DIL) chip carrier, flip chip, and tape carrier methods are employed.
Of these methods, those which are high in reliability at the connecting portions and can present small and thin packages include the flip chip and tape carrier method. In the flip chip methods, a multilayer metal film called barrier metal is provided on electrode terminals on a semiconductor element, and metal bumps are provided on this multilayer metal film by an electroplating method.
On the other hand, in the case of the film carrier method, like in the flip chip method, metal bumps are provided through barrier metal on electrodes on a semiconductor device by the electroplating method. Metal leads are provided on a long polyimide tape with a specific width, and metal bumps on electrodes of a semiconductor element and metal leads are simultaneously connected at the same time, regardless of the number of electrodes.
However, these flip chip and tape carrier methods have the following drawbacks.
The flip chip and tape carrier methods require, as processes for forming metal bumps on electrodes of a semiconductor device, a deposition process for forming multi-layer electrode film, a photo-lithography process for forming a mask for electroplating, a plating process for forming metal bumps by electroplating, and an etching process for removing the unnecessary multi-layer electrode film. These processes injure a semiconductor device and thereby, the yield rate is lowered and the cost for forming metal bumps is increased. Further in the case of the flip chip method, since metal bumps are directly connected to wiring patterns of a circuit board, heat expansion and mechanical distortion, once occurred, are not relaxed and thereby, injure connecting portion of the metal bumps, and the semiconductor device itself so that electrical inferiority often occurs. On the other hand, in case of the film carrier method, metal bumps, which are formed on electrode terminals of a semiconductor device, are connected to metal leads, and then, electrical measurement is conducted by use of the metal leads, and thereafter, the metal leads are cut in predetermined length to be connected to the wiring patterns of the circuit board. Therefore, the film carrier method solves problems of the flip chip method, i.e., heat expansion and mechanical distortion of a circuit board etc., and the heat expansion etc., are relaxed by the metal lead so that a high reliability of connection is obtained. However, the manufacturing cost of carrier film, i.e., polyimide tape, on which metal leads are formed is extremely expensive so that the use of the film carrier method cannot become popular.